linux-kernel - [PATCH 5.7 123/265] dma-direct: check return value when encrypting or decrypting memory

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Date:   Mon, 29 Jun 2020 11:15:56 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     David Rientjes <rientjes@...gle.com>,
        Christoph Hellwig <hch@....de>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.7 123/265] dma-direct: check return value when encrypting or decrypting memory

From: David Rientjes <rientjes@...gle.com>

[ Upstream commit 56fccf21d1961a06e2a0c96ce446ebf036651062 ]

__change_page_attr() can fail which will cause set_memory_encrypted() and
set_memory_decrypted() to return non-zero.

If the device requires unencrypted DMA memory and decryption fails, simply
free the memory and fail.

If attempting to re-encrypt in the failure path and that encryption fails,
there is no alternative other than to leak the memory.

Fixes: c10f07aa27da ("dma/direct: Handle force decryption for DMA coherent buffers in common code")
Signed-off-by: David Rientjes <rientjes@...gle.com>
Signed-off-by: Christoph Hellwig <hch@....de>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 kernel/dma/direct.c | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 4e789c46ff0bf..98c445dcb308b 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -124,6 +124,7 @@ void *dma_direct_alloc_pages(struct device *dev, size_t size,
 {
 	struct page *page;
 	void *ret;
+	int err;
 
 	if (IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) &&
 	    dma_alloc_need_uncached(dev, attrs) &&
@@ -176,8 +177,12 @@ void *dma_direct_alloc_pages(struct device *dev, size_t size,
 	}
 
 	ret = page_address(page);
-	if (force_dma_unencrypted(dev))
-		set_memory_decrypted((unsigned long)ret, 1 << get_order(size));
+	if (force_dma_unencrypted(dev)) {
+		err = set_memory_decrypted((unsigned long)ret,
+					   1 << get_order(size));
+		if (err)
+			goto out_free_pages;
+	}
 
 	memset(ret, 0, size);
 
@@ -196,9 +201,13 @@ done:
 	return ret;
 
 out_encrypt_pages:
-	if (force_dma_unencrypted(dev))
-		set_memory_encrypted((unsigned long)page_address(page),
-				     1 << get_order(size));
+	if (force_dma_unencrypted(dev)) {
+		err = set_memory_encrypted((unsigned long)page_address(page),
+					   1 << get_order(size));
+		/* If memory cannot be re-encrypted, it must be leaked */
+		if (err)
+			return NULL;
+	}
 out_free_pages:
 	dma_free_contiguous(dev, page, size);
 	return NULL;
-- 
2.25.1